One of the specifications for playback of a DVD (Digital Versatile Disc) is that of a DVD video format. With the DVD video format, content data such as video or audio is multiplexed along with various types of sub-picture data such as subtitles, and are recorded on the disk as a program stream. Also, navigation data for playing back such stream interactively is stored on the disk. Such technology is disclosed in for example Patent Document 1, Patent Document 2, and so forth.
Here, interactive playback refers to playback such as playback from a desired position or in a desired order, as well as playback wherein a user uses various types of functionality of a DVD, such as a multi-angle function which can play back a moving image which is image-captured from various angles, a multi-language function which can play back in a desired language from multiple languages, a parental control function which does not perform playback of certain scenes such as violence scenes, and the like.
A program stream can multiplex multiple audio streams and multiple subtitle data streams. Thus, for example, data for subtitles in multiple different languages can be recorded onto one disk as to one video content such as a movie, and the user can select the audio of the desired language or subtitles before starting playback or during playback of the video.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-140662
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2002-311967